Structural Improvement And Performance Research Of Safety Brake For Tower Crane

The tower crane has the characteristics of high lifting height,large lifting capacity,good speed regulation performance and wide coverage arge,and is widely used in the construction of high-rise and super high-rise buildings.Therefore,the accident rate of construction sites is higher than that in other industries and most accidents are related to construction equipment.Due to the large structure and the high operation altitude,serious casualties are easy to happen for the tower crane.There are many types of tower crane accidents,in which brake device damage is the most common one.The early working braking for hoisting machinery are generally completed by brakes placed on the high speed shaft of the drive mechanism,If some faults come out for the rear transmission chain such as the broken shaft,the broken key of the coupling or the broken gear of the gearbox,and the huge safety accident may be caused.For safety operation,the tower crane safety brake is gradually put into use.In recent years,our countries has revised the relevant crane machinery standards design specifications and related safety regulations in which the requirement for the low speed shaft installing safety protection brake in the lifting mechanism was proposed.In GB/T3811-2008?Crane design specification?,TSGQ0002-2008?Safety inspection specification for hsisting machinrry-bridge crane?and many other regulations,there are clear statements for safety brakes.At present,the most used safety brakes for tower crane hoisting mechanisms are hydraulic caliper disc brakes.The reliability of its performance is critical to the stable operation of the tower crane and the personal safety of the operators.However,in actual use,the large braking shock still exists during the upper brake process which affects the service life of the friction plate,and the holding time for the system is still short which cause the frequent start of the pump and lead to low service life of motor and pump.In this thesis,the structure and working principle of the SBD240-D hydraulic caliper disc brake are introduced.Aiming at solving the problem of large brake impact during the actual work of the tower crane safety brake,First of all,solidworks and Adams software are used to establish the multi-body dynamics simulation model of the safety brake,and the dynamics process of the safety brake is simulated under the rated clamping force condition.At the same time,the problem of short holding time of the system is also analyzed.On this basis,the related issues was improved with the help of TRIZ theory;Second,combined with experiment to discuss the effect of friction plates on braking performance.At last,The ANSYS software is used to check the strength of the brake arm under dynamic load conditions and make adaptive adjustments.Simulation results for the improved caliper disc brakes indicate that the braking shock during the upper brake process is reduced by 44%and the brake response time is shortened by 50%,which extend the service life of the friction plate.The improvement of the locating device also simplifies the mechanism and structure of the original brake;The structural improvement of the brake arm eliminates the stress concentration and reduces the material loss under the premise of ensuring the structural strength;in the actual application process,the pressure retention time of the improved hydraulic drive system is extended from the original half an hour to one hour,avoiding The drive motor starts frequently,reducing energy consumption and extending the effective life of the system.